Enzymatic Synthesis and Purification of Galactosylated Chitosan Oligosaccharides Reducing Adhesion of Enterotoxigenic Escherichia coli K88

Bioactive peptides in hydrolysates of bovine and camel milk proteins: A review of studies on peptides that reduce blood pressure, improve glucose homeostasis, and inhibit pathogen adhesion

The prevalence of diet-related chronic conditions including hypertension and cardiovascular disease, and diabetes mellitus has increased worldwide. Research regarding the use of food-derived bioactive peptides as an alternative strategy to mitigate chronic diseases is on the rise. Milk is recognized as one of the main dietary protein sources for health beneficial bioactive compounds. Hundreds of in vitro studies have suggested that milk-derived bioactive peptides offer multiple biological and physiological benefits, and some but not all were confirmed in vivo with animal models for hypertension, hyperglycemia, and pathogen adhesion. However, only a limited number of health benefits have been confirmed by randomized clinical trials. This review provides an overview of the current clinical studies that target hypertension, postprandial hyperglycemic, and adhesion of enteric pathogen with bioactive peptides derived from bovine and camel milk, with a focus on the factors affecting the efficacy of orally ingested products.

Galacto-oligosaccharides fed during gestation increase Rotavirus A specific antibodies in sow colostrum, modulate the microbiome, and reduce infectivity in neonatal piglets in a commercial farm setting

Introduction

Rotavirus A is a major cause of acute dehydrating diarrhea in neonatal pigs resulting in significant mortality, morbidity, reduced performance and economic loss. Commercially available prebiotic galacto-oligosaccharides are similar to those of mammalian milk and stimulate the development of the microbiota and immune system in neonates. Little is known about the effects of supplementing sows' diets with galacto-oligosaccharides during gestation. This study aimed to determine if dietary galacto-oligosaccharide supplementation during gestation could improve immunity, reduce rotavirus infection and modulate the microbiota in sows and neonates in a commercial farm setting with confirmed natural endemic rotavirus challenge.

Methods

In a randomized controlled trial, control sows received lactation diet with no galacto-oligosaccharide supplementation and test sows received lactation diet with 30 g/day galacto-oligosaccharide top-dressed into feed daily, seven days before farrowing. Colostrum was collected from sows 24 hours post-partum and tested for rotavirus specific antibodies. Fecal samples were collected from sows and piglets three days post-partum, tested for rotavirus A by qPCR and the microbiome composition assessed by 16s rRNA gene sequencing.

Results

Supplementation with galacto-oligosaccharides during gestation significantly increased rotavirus-specific IgG and IgA in sow colostrum and reduced the number of rotavirus positive piglet fecal samples. Abundance of potential pathogens Treponema and Clostridiales were higher in fecal samples from non-galacto-oligosaccharide fed sows, their piglets and rotavirus positive samples.

Discussion

This study demonstrates that galacto-oligosaccharide supplementation during gestation significantly increases rotavirus specific IgG and IgA in sow colostrum thereby reducing neonatal rotavirus infection and suppresses potential pathogenic bacteria in nursing sows and neonatal piglets.

Galacto-Oligosaccharides Increase the Abundance of Beneficial Probiotic Bacteria and Improve Gut Architecture and Goblet Cell Expression in Poorly Performing Piglets, but Not Performance

Poorly performing piglets receiving commercial milk replacers do not benefit from the naturally occurring probiotic galacto-oligosaccharides otherwise found in sow milk. Study objectives were to investigate the effects of complete milk replacer supplemented with galacto-oligosaccharides on the microbiome, gut architecture and immunomodulatory goblet cell expression of poorly performing piglets that could benefit from milk replacement feeding when separated from sows and housed with fit siblings in environmentally controlled pens. The study is novel in that it is one of the first to investigate the effects of supplementing complete milk replacer with galacto-oligosaccharides in poorly performing piglets. Gastrointestinal tract samples were collected from piglets, and the microbiome composition was assessed by 16s ribosomal ribonucleic acid gene sequencing. Gut architectural features, villus/crypt ratio and enumeration of goblet cells in tissues were assessed by histopathological techniques. The most abundant taxa identified at the genus level were Lactobacillus, Streptococcus, Prevotella, Lactococcus and Leuconostoc. Milk replacer plus galacto-oligosaccharides significantly improved gut architectural features and villus/crypt ratio throughout the gastrointestinal tract, increased the number of goblet cells and revealed a differential abundance of beneficial probiotic bacteria, particularly Lactobacillus and Bifidobacterium. In these respects, galacto-oligosaccharide-supplemented milk replacer may be a useful addition to animal husbandry in poorly performing, non-thriving animals when moved to environmentally controlled pens away from sows and fit siblings, thereby modulating the microbiome and gastrointestinal tract performance.

The dietary fibre rhamnogalacturonan improves intestinal epithelial barrier function in a microbiota-independent manner

BACKGROUND AND PURPOSE

Dietary fibre comprises a complex group of polysaccharides that are indigestible but are fermented by gut microbiota, promoting beneficial effects to the intestinal mucosa indirectly through the production of short chain fatty acids. We found that a polysaccharide, rhamnogalacturonan (RGal), from the plant Acmella oleracea, has direct effects on intestinal epithelial barrier function. Our objective was to determine the mechanism whereby RGal enhances epithelial barrier function.

EXPERIMENTAL APPROACH

Monolayers of colonic epithelial cell lines (Caco-2, T84) and of human primary cells from organoids were mounted in Ussing chambers to assess barrier function. The cellular mechanism of RGal effects on barrier function was determined using inhibitors of TLR-4 and PKC isoforms.

KEY RESULTS

Apically applied RGal (1000 μg/ml) significantly enhanced barrier function as shown by increased transepithelial electrical resistance (TER) and reduced fluorescein isothiocyanate (FITC)-dextran flux in Caco-2, T84 and human primary cell monolayers, and accelerated tight junction reassembly in Caco-2 cells in a calcium switch assay. RGal also reversed the barrier-damaging effects of inflammatory cytokines on FITC-dextran flux and preserved the tight junction distribution of occludin. RGal activated TLR4 in TLR4-expressing HEK reporter cells, an effect that was significantly inhibited by the TLR4 inhibitor, C34. The effect of RGal was also dependent on PKC, specifically the isoforms PKCd and PKCζ.

CONCLUSION AND IMPLICATIONS

RGal enhances intestinal epithelial barrier function through activation of TLR4 and PKC signaling pathways. Elucidation of RGal mechanisms of action could lead to new, dietary approaches to enhance mucosal healing in inflammatory bowel diseases.

Low molecular weight chitosan oligosaccharides (LMW-COSs) prevent obesity-related metabolic abnormalities in association with the modification of gut microbiota in high-fat diet (HFD)-fed mice

In this study, the two enzymatic low molecular weight chitosan oligosaccharides (LMW-COSs), LMW-COS-H and LMW-COS-L, were prepared with average MWs of 879.6 Da and 360.9 Da, respectively. Compared to LMW-COS-L, the LMW-COS-H was more effective in improving high-fat diet (HFD)-induced metabolic abnormalities, such as obesity, hyperlipidemia, low-grade inflammation and insulin resistance. The subsequent analysis of gut microbiota showed that the supplement of LMW-COSs caused overall structural and genus/species-specific changes in the gut microbiota, which were significantly correlated with the metabolic parameters. Specifically, both of the LMW-COSs significantly decreased the relative abundance of inflammatory bacteria such as Erysipelatoclostridium and Alistipes, whereas that of the beneficial intestinal bacteria (such as Akkermansia and Gammaproteobacteria) increased significantly. This study suggested that there were potential prebiotic functions of LMW-COSs in HFD fed mice, which regulated the dysfunctional gut microbiota, alleviated low-grade inflammation and maintained the intestinal epithelial barrier.

Natural and engineered transglycosylases: Green tools for the enzyme-based synthesis of glycoproducts

An increasing number of transglycosylase-based processes provide access to oligosaccharides or glycoconjugates, some of them reaching performance levels compatible with industrial developments. Nevertheless, the full potential of transglycosylases has not been explored because of the challenges in transforming a glycoside hydrolase into an efficient transglycosylase. Advances in studying enzyme structure/function relationships, screening enzyme activity, and generating synthetic libraries guided by computational protein design or machine learning methods should considerably accelerate the development of these catalysts. The time has now come for researchers to uncover their possibilities and learn how to design and precisely refine their activity to respond more rapidly to the growing demand for well-defined glycosidic structures.

Expression and characterization of a novel glycoside hydrolase family 46 chitosanase identified from marine mud metagenome

A novel chitosanase gene, csn4, was identified through function-based screening of a marine mud metagenomic library. The encoded protein, named CSN4, which belonged to glycoside hydrolase family 46, showed its maximum identity (79%) with Methylobacter tundripaludum peptidoglycan-binding protein. CSN4 was expressed in Escherichia coli and purified. It displayed maximal activity at 30 °C and pH 7. A weakly-alkaline solution strongly inhibited the activity. The enzymatic activity was enhanced by addition of Mn²⁺ or Co²⁺. CSN4 exhibited strict substrate specificity for chitosan, and the activity was enhanced by increasing the degree of deacetylation. Thin-layer chromatography and electrospray ionization-mass spectrometry showed that CSN4 displayed an endo-type cleavage pattern, hydrolyzing chitosan mainly into (GlcN)₂, (GlcN)₃ and (GlcN)₄. The novel characteristics of the chitosanase CSN4 make it a potential candidate to produce chitooligosaccharides from chitosan in industry.

Shaping the Infant Microbiome With Non-digestible Carbohydrates

Natural polysaccharides with health benefits are characterized by a large structural diversity and differ in building blocks, linkages, and lengths. They contribute to human health by functioning as anti-adhesives preventing pathogen adhesion, stimulate immune maturation and gut barrier function, and serve as fermentable substrates for gut bacteria. Examples of such beneficial carbohydrates include the human milk oligosaccharides (HMOs). Also, specific non-digestible carbohydrates (NDCs), such as galacto-oligosaccharides (GOS) and fructo-oligosaccharides (FOS) are being produced with this purpose in mind, and are currently added to infant formula to stimulate the healthy development of the newborn. They mimic some functions of HMO, but not all. Therefore, many research efforts focus on identification and production of novel types of NDCs. In this review, we give an overview of the few NDCs currently available [GOS, FOS, polydextrose (PDX)], and outline the potential of alternative oligosaccharides, such as pectins, (arabino)xylo-oligosaccharides, and microbial exopolysaccharides (EPS). Moreover, state-of-the-art techniques to generate novel types of dietary glycans, including sialylated GOS (Sia-GOS) and galactosylated chitin, are presented as a way to obtain novel prebiotic NDCs that help shaping the infant microbiome.

Discovery and Characterization of a Novel Chitosanase from Paenibacillus dendritiformis by Phylogeny-Based Enzymatic Product Specificity Prediction

In the process of genome mining for novel chitosanases by phylogeny-based enzymatic product specificity prediction, a gene named Csn-PD from Paenibacillus dendritiformis was discovered. The enzyme was classified as a member of the GH46 family of glycoside hydrolase based on sequence alignment, and it was functionally expressed in Escherichia coli BL21 (DE3). The recombinant chitosanase was purified, and its molecular weight was estimated to be 31 kDa by SDS-PAGE. Csn-PD displayed maximal activity toward colloidal chitosan at pH 7.0 and 45 °C, respectively. A combination of thin-layer chromatography and electrospray ionization-mass spectrometry results showed that Csn-PD exhibited an endotype cleavage pattern and hydrolyzed chitosan to yield (GlcN)₂ as the major product. The unique enzymatic properties of this chitosanase may make it a good candidate for (GlcN)₂ production.

Enzyme and microbial technology for synthesis of bioactive oligosaccharides: an update

Oligosaccharides, in either free or bound forms, play crucial roles in a wide range of biological processes. Increasing appreciation of their roles in cellular communication, interaction, pathogenesis, and prebiotic functions has stimulated tremendous interests in their synthesis. Pure and structurally defined oligosaccharides are essential for fundamental studies. On the other hand, for those with near term medical and nutraceutical applications, their large-scale synthesis is necessary. Unfortunately, oligosaccharides are notoriously difficult in their synthesis, and their enormous diverse structures leave a vast gap between what have been synthesized in laboratory and those present in various biological systems. While enzymes and microbes are nature's catalysts for oligosaccharides, their effective use is not without challenges. Using examples of galactose-containing oligosaccharides, this review analyzes the pros and cons of these two forms of biocatalysts and provides an updated view on the status of biocatalysis in this important field. Over the past few years, a large number of novel galactosidases were discovered and/or engineered for improved synthesis via transglycosylation. The use of salvage pathway for regeneration of uridine diphosphate (UDP)-galactose has made the use of Leloir glycosyltransferases simpler and more efficient. The recent success of large-scale synthesis of 2' fucosyllactose heralded the power of whole-cell biocatalysis as a scalable technology. While it still lags behind enzyme catalysis in terms of the number of oligosaccharides synthesized, an acceleration in the use of this form of biocatalyst is expected as rapid advances in synthetic biology have made the engineering of whole cell biocatalysts less arduous and less time consuming.